Vegetable protein materials are well known as adhesive binders for paper coating compositions containing pigments. The paper coating compositions provide the paper with a desirable finish, gloss, smoothness, and microporous surface. The functions of the pigment in the coating composition are to fill irregularities of the paper surface and to produce an even and uniformly absorbent surface for printing. The adhesive functions to bind the pigment particles to each other as well as to the surface of the base paper.
Particularly preferred vegetable protein materials for use as adhesive binders in paper coating compositions are modified soy proteins. These adhesive binders are typically prepared from an isolated soy protein modified by hydrolysis and other chemical treatments to prepare a protein adhesive material suitable for use as a binder in paper coating compositions.
Although such compositions have found wide usage in the paper coating industry, it would be desirable to provide improved vegetable protein binders which can be used at lower levels in paper coating compositions to achieve suitable rheological properties in the coating compositions while also exhibiting functional properties comparable to conventional paper coating compositions.